2 Loads and Structural Stress Because of the energy content of the wind is relative to the cube of the wind speed, turbine blades exposed to wind speeds will be under an enormous amount of stress. In order to diminish the impact of wind speeds, turbine manufacturers develop the rotors on them with few blades somehow they are as narrow and long as practical (Pinting ZHANG and Shuhong HUANG 2011). The maximum efficiency from such blades can be attained based on the pitch at an optimum angle to the wind, respectively (A.K.Wright and D. H.Wood 2004). All the necessary information with respect to the loads and especially directions are presented obviously in Fig.1.Note that the chordwise direction is frequently known as the edgewise direction.
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Supposing steady, uniform axisymmetric incompressible, and inviscid flow with a nonrotating wake, the mass conservation provides the following relation: ρU_1 A_1= ρU_2 A_d=ρU_4 A_4 (6)
As is apparent, Ad is the area of the actuator disk.
Fig 2. Actuator disk model of a wind turbine (Xiaomin Chen and Ramesh Agarwal, 2014)
The axial induction factor a, since the actuator disk induces velocity in the stream tube, can be expressed by:
a=(U_1-U_2)/U_1
Supposing steady, uniform axisymmetric incompressible, and inviscid flow with a nonrotating wake, the mass conservation provides the following relation: ρU_1 A_1= ρU_2 A_d=ρU_4 A_4 (6)
As is apparent, Ad is the area of the actuator disk.
Fig 2. Actuator disk model of a wind turbine (Xiaomin Chen and Ramesh Agarwal, 2014)
The axial induction factor a, since the actuator disk induces velocity in the stream tube, can be expressed by:
a=(U_1-U_2)/U_1